Collection Of Mononuclear Cells And Peripheral Blood Stem Cells

ABSTRACT

Blood in a separation chamber is separated into a red blood cell layer, a plasma constituent, and a mononuclear cell-containing layer. A portion of the plasma constituent exits the chamber via a plasma outlet, while a first portion of the red blood cell layer exits via a red blood cell outlet. A second portion of the red blood cell layer exits the chamber via the red blood cell outlet and is collected. At least a portion of the collected red blood cell layer may then be conveyed to the chamber via the red blood cell outlet to convey at least a portion of the mononuclear cell-containing layer out of the chamber via the plasma outlet for collection. A second portion of the plasma constituent may be conveyed out of the chamber via the plasma outlet to more fully collect the mononuclear cell-containing layer without the use of collected plasma.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of and priority of U.S. Provisional Patent Application Ser. No. 62/814,033, filed Mar. 5, 2019, the contents of which are incorporated by reference herein.

BACKGROUND Field of the Disclosure

The present disclosure relates to collection of mononuclear cells (“MNCs”) and peripheral blood stem cells. More particularly, the present disclosure relates to improvements to the MNC transfer and plasma flush phases of an MNC collection procedure.

Description of Related Art

Various blood processing systems now make it possible to collect particular blood constituents, rather than whole blood, from a blood source. Typically, in such systems, whole blood is drawn from a source, the particular blood component or constituent is removed and collected, and the remaining blood constituents are returned to the source.

Whole blood is typically separated into its constituents through centrifugation. This requires that the whole blood be passed through a centrifuge after it is withdrawn from, and before it is returned to, the source. To avoid contamination and possible infection of the source, the blood is preferably contained within a sealed, sterile fluid flow system during the entire centrifugation process. Typical blood processing systems thus include a permanent, reusable centrifuge assembly containing the hardware (drive system, pumps, valve actuators, programmable controller, and the like) that spins and pumps the blood, and a disposable, sealed and sterile fluid processing assembly that is mounted in cooperation on the hardware. The centrifuge assembly engages and spins a disposable centrifuge chamber of the fluid processing assembly during a collection procedure. The blood, however, makes actual contact only with the fluid processing assembly, which assembly is used only once and then discarded.

As the whole blood is spun by the centrifuge, the heavier (greater specific gravity) components, such as red blood cells, move radially outwardly away from the center of rotation toward the outer or “high-G” wall of the separation chamber. The lighter (lower specific gravity) components, such as plasma, migrate toward the inner or “low-G” wall of the separation chamber. Various ones of these components can be selectively removed from the whole blood by forming appropriately located channeling seals and outlet ports in the separation chamber.

An exemplary method of centrifugally separating and collecting MNCs is described in U.S. Pat. No. 5,980,760, which is incorporated herein by reference. In such a procedure, whole blood in a centrifuge is separated into platelet-poor plasma, an interface or MNC-containing layer, and packed red blood cells. The platelet-poor plasma is collected for later use, while the packed red blood cells are returned to the blood source and the MNC-containing layer remains in the centrifuge. When a target amount of platelet-poor plasma has been collected, an MNC accumulation phase begins. During this phase, the position of the interface within the centrifuge is moved closer to the low-G wall, such that platelet-rich plasma and packed red blood cells are removed from the centrifuge while the MNC-containing layer continues to build up in the centrifuge. Portions of the platelet-rich plasma and the packed red blood cells are returned to the blood source, with the remainder of the platelet-rich plasma and packed red blood cells being recirculated through the centrifuge to maintain a proper hematocrit.

When a certain amount of blood has been processed, the return and recirculation of the packed red blood cells is ended and a red blood cell collection phase begins. During this phase, recirculation and return of the platelet-rich plasma continues, while the packed red blood cells are conveyed from the centrifuge via an outlet port to a red blood cell collection container for later use.

When a target amount of packed red blood cells has been collected, an MNC harvest phase begins. To harvest the MNCs in the MNC-containing layer, the packed red blood cells are temporarily prevented from exiting the centrifuge. At least a portion of the collected red blood cells is conveyed into the centrifuge via the same inlet port by which whole blood had previously been flowing into the centrifuge, which forces the MNC-containing layer to exit the centrifuge via the same outlet as the platelet-rich plasma. The platelet-rich plasma exiting the centrifuge ahead of the MNC-containing layer is directed into the platelet-poor plasma container, with the MNC-containing layer subsequently being directed into an MNC collection container.

Following the MNC harvest phase, a plasma flush phase begins. During this phase, plasma from the platelet-poor plasma container is used to flush any MNC-containing layer positioned between the separation chamber and the MNC collection container back into the separation chamber. The MNC-containing layer flushed back into the separation chamber may be subsequently collected by repeating the various phases, until a target amount of MNC product has been collected. Following collection, the MNC product may be treated to further processing, such as extracorporeal photopheresis.

SUMMARY

There are several aspects of the present subject matter which may be embodied separately or together in the devices and systems described and claimed below. These aspects may be employed alone or in combination with other aspects of the subject matter described herein, and the description of these aspects together is not intended to preclude the use of these aspects separately or the claiming of such aspects separately or in different combinations as set forth in the claims appended hereto.

In one aspect, a fluid processing system includes a centrifuge configured to receive a separation chamber of a fluid processing assembly. The system also includes a plurality of pumps configured to convey fluids through the fluid processing assembly and a controller. The controller is configured to actuate at least one of the plurality of pumps to convey blood into the centrifuge via an inlet; actuate the centrifuge to separate the blood in the centrifuge into a red blood cell layer, a plasma constituent, and a mononuclear cell-containing layer; and actuate at least one of the plurality of pumps to convey a portion of the plasma constituent from the centrifuge via a plasma outlet and to convey a first portion of the red blood cell layer from the centrifuge via a red blood cell outlet while allowing a volume of the mononuclear cell-containing layer to increase in the centrifuge. The controller is further configured to actuate at least one of the plurality of pumps to convey a second portion of the red blood cell layer from the centrifuge via the red blood cell outlet to a red blood cell collection container of the fluid processing assembly, and actuate at least one of the plurality of pumps to convey at least a portion of the contents of the red blood cell collection container to the centrifuge via the red blood cell outlet to convey at least a portion of the mononuclear cell-containing layer out of the centrifuge for collection.

In another aspect, a method is provided for collecting mononuclear cells. The method includes separating blood in a separation chamber into a red blood cell layer, a plasma constituent, and a mononuclear cell-containing layer and conveying a portion of the plasma constituent from the separation chamber via a plasma outlet while conveying a first portion of the red blood cell layer from the separation chamber via a red blood cell outlet and while allowing a volume of the mononuclear cell-containing layer to increase in the separation chamber. A second portion of the red blood cell layer is conveyed from the separation chamber via the red blood cell outlet to a red blood cell collection container and then at least a portion of the contents of the red blood cell collection container is conveyed to the separation chamber via the red blood cell outlet to convey at least a portion of the mononuclear cell-containing layer out of the separation chamber for collection.

In yet another aspect, a fluid processing system includes a centrifuge configured to receive a separation chamber of a fluid processing assembly. The system also includes a plurality of pumps configured to convey fluids through the fluid processing assembly and a controller. The controller is configured to actuate at least one of the plurality of pumps to convey blood into the centrifuge via an inlet; actuate the centrifuge to separate the blood in the centrifuge into a red blood cell layer, a plasma constituent, and a mononuclear cell-containing layer; and actuate at least one of the plurality of pumps to convey a portion of the plasma constituent from the centrifuge via a plasma outlet and to convey a first portion of the red blood cell layer from the centrifuge via a red blood cell outlet while allowing a volume of the mononuclear cell-containing layer to increase in the centrifuge. The controller is further configured to actuate at least one of the plurality of pumps to convey a second portion of the red blood cell layer from the centrifuge via the red blood cell outlet to a red blood cell collection container of the fluid processing assembly, actuate at least one of the plurality of pumps to convey at least a portion of the contents of the red blood cell collection container to the centrifuge to convey at least a portion of the mononuclear cell-containing layer out of the centrifuge via the plasma outlet for collection, and actuate at least one of the plurality of pumps to convey plasma from the centrifuge via the plasma outlet to more fully collect said at least a portion of the mononuclear cell-containing layer without the use of collected plasma.

In another aspect, a method is provided for collecting mononuclear cells. The method includes separating blood in a separation chamber into a red blood cell layer, a plasma constituent, and a mononuclear cell-containing layer and conveying a portion of the plasma constituent from the separation chamber via a plasma outlet while conveying a first portion of the red blood cell layer from the separation chamber via a red blood cell outlet and while allowing a volume of the mononuclear cell-containing layer to increase in the separation chamber. A second portion of the red blood cell layer is conveyed from the separation chamber via the red blood cell outlet to a red blood cell collection container and then at least a portion of the contents of the red blood cell collection container is conveyed to the separation chamber to convey at least a portion of the mononuclear cell-containing layer out of the separation chamber for collection. Plasma is conveyed from the separation chamber via the plasma outlet to more fully collect said at least a portion of the mononuclear cell-containing layer without the use of collected plasma.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an exemplary blood separation device that comprises a component of a blood separation system according to an aspect of the present disclosure;

FIG. 2 is a schematic view of an exemplary disposable fluid flow circuit that may be mounted to the blood separation device of FIG. 1 to complete a blood separation system according to an aspect of the present disclosure;

FIG. 3 is a perspective view of an exemplary centrifugal separator of the blood separation device of FIG. 1, with the centrifugal separation chamber of a fluid flow circuit mounted therein;

FIG. 4 is a top plan view of an exemplary cassette of a fluid flow circuit, which can be actuated to perform a variety of different blood processing procedures in association with the blood separation device shown in FIG. 1;

FIG. 5 is a perspective view of the centrifugal separator of FIG. 3, with selected portions thereof broken away to show a light source of an interface monitoring system;

FIG. 6 is a perspective view of the centrifugal separator of FIG. 3, with the light source operating to transmit a light beam to a light detector of the interface monitoring system;

FIG. 7 is a perspective view of the centrifugal separator of FIG. 3, with selected portions thereof broken away to show the light source and light detector of the interface monitoring system;

FIG. 8 is a perspective view of an exemplary centrifugal separation chamber of a fluid flow circuit;

FIG. 9 is a front elevational view of the centrifugal separation chamber of FIG. 8;

FIG. 10 is a bottom perspective view of the fluid flow path through the centrifugal separation chamber of FIG. 8;

FIG. 11 is a perspective view of another embodiment of a centrifugal separation chamber of a fluid flow circuit;

FIG. 12 is a front elevational view of the centrifugal separation chamber of FIG. 11;

FIG. 13 is a top perspective view of the fluid flow path through the centrifugal separation chamber of FIG. 11;

FIG. 14 is a perspective view of a third embodiment of a centrifugal separation chamber of a fluid flow circuit;

FIG. 15 is a front elevational view of the centrifugal separation chamber of FIG. 14;

FIG. 16 is an enlarged perspective view of a portion of a channel of any of the centrifugal separation chambers of FIGS. 8-15, with an interface between separated blood components being positioned at a (typically) desired location on a ramp defined within the channel;

FIG. 17 is an enlarged perspective view of the channel and ramp of FIG. 16, with the interface being at a (typically) undesired high location on the ramp;

FIG. 18 is an enlarged perspective view of the channel and ramp of FIG. 16, with the interface being at a (typically) undesired low location on the ramp;

FIG. 19 is a perspective view of a prismatic reflector used in combination with any of the centrifugal separation chambers of FIGS. 8-15;

FIG. 20 is a perspective view of the prismatic reflector of FIG. 19, showing light being transmitted therethrough;

FIGS. 21-24 are diagrammatic views of the ramp and prismatic reflector of the centrifugal separation chamber passing through the path of light from the light source during a calibration phase;

FIGS. 25-28 are diagrammatic views of the voltage output or signal transmitted by the light detector during the conditions shown in FIGS. 21-24, respectively;

FIGS. 29-32 are diagrammatic views of the ramp and prismatic reflector passing through the path of light from the light source during a separation procedure;

FIGS. 33-36 are diagrammatic views of the voltage output or signal transmitted by the light detector during the conditions shown in FIGS. 29-32, respectively;

FIGS. 37 and 38 are diagrammatic views of separated blood components on the ramp and the pulse widths of a signal generated by the light detector for each condition;

FIG. 39 is a diagrammatic view of saline on the ramp and the pulse width of a signal generated by the light detector for such a condition;

FIG. 40 is a diagrammatic view of the position of an interface between separated blood components on the ramp compared to a target interface position; and

FIGS. 41-47 are schematic views of the fluid circuit of FIG. 2, showing the system carrying out different fluid flow tasks in connection with separation and collection of mononuclear cells and peripheral blood stem cells.

DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

The embodiments disclosed herein are for the purpose of providing a description of the present subject matter, and it is understood that the subject matter may be embodied in various other forms and combinations not shown in detail. Therefore, specific designs and features disclosed herein are not to be interpreted as limiting the subject matter as defined in the accompanying claims.

FIGS. 1-47 show components of a blood or fluid separation system that embodies various aspects of the present subject matter. Generally speaking, the system includes two principal components, a durable and reusable blood separation device 10 (FIG. 1) and a disposable fluid flow circuit 12 (FIG. 2). The blood separation device 10 includes a spinning membrane separator drive unit 14 (FIG. 1), a centrifuge or centrifugal separator 16 (FIG. 3), additional components that control fluid flow through the disposable flow circuit 12, and a controller 18 (FIG. 1), which governs the operation of the other components of the blood separation device 10 to perform a blood processing and collection procedure selected by the operator, as will be described in greater detail

I. The Durable Blood Separation Device

The blood separation device 10 (FIG. 1) is configured as a durable item that is capable of long-term use. It should be understood that the blood separation device 10 of FIG. 1 is merely exemplary of one possible configuration and that blood separation devices according to the present disclosure may be differently configured. For example, it is within the scope of the present disclosure for the blood separation device to omit a spinning membrane separator drive unit 14 and to include only a centrifugal separator 16.

In the illustrated embodiment, the blood separation device 10 is embodied in a single housing or case 20. The illustrated case 20 includes a generally horizontal portion 22 (which may include an inclined or angled face or upper surface for enhanced visibility and ergonomics) and a generally vertical portion 24. The spinning membrane separator drive unit 14 and the centrifugal separator 16 are shown as being incorporated into the generally horizontal portion 22 of the case 20, while the controller 18 is shown as being incorporated into the generally vertical portion 24. The configuration and operation of the centrifugal separator 16, the controller 18, and selected other components of the blood separation device 10 will be described in greater detail.

In the illustrated embodiment, the generally horizontal portion 22 is intended to rest on an elevated, generally horizontal support surface (e.g., a countertop or a tabletop), but it is also within the scope of the present disclosure for the case 20 to include a support base to allow the case 20 to be appropriately positioned and oriented when placed onto a floor or ground surface. It is also within the scope of the present disclosure for the case 20 to be mounted to a generally vertical surface (e.g., a wall), by either fixedly or removably securing the generally vertical portion 24 of the case 20 to the surface.

The case 20 may be configured to assume only the position or configuration of FIG. 1 or may be configured to move between two or more positions or configurations. For example, in one embodiment, the generally horizontal and vertical portions 22 and 24 are joined by a hinge or pivot, which allows the case 20 to be moved between a functional or open configuration (FIG. 1) in which the generally vertical portion 24 is oriented at approximately 90 degrees to the generally horizontal portion 22 and a transport or closed configuration in which the generally vertical portion 24 is rotated about the hinge to approach the generally horizontal portion 22. In such a reconfigurable embodiment, the generally vertical portion 24 may be considered to be the lid of the case 20, while the generally horizontal portion 22 may be considered to be the base. If the case 20 is so reconfigurable, then it may include a latch for releasably locking the case 20 in its closed configuration and/or a handle, which the operator can grasp for transporting the case 20 in its closed configuration.

While it may be advantageous for the blood separation device 10 to be embodied in a compact, portable case 20, it is also within the scope of the present disclosure for the blood separation device to be embodied in a larger case or fixture that is intended to be installed in a single location and remain in that location for an extended period of time. If the blood separation device is provided as a fixture, it may be provided with more components and functionality than a more portable version.

A. Spinning Membrane Separator Drive Unit

The illustrated blood separation device 10 includes a spinner support or spinning membrane separator drive unit 14 (FIG. 1) for accommodating a generally cylindrical spinning membrane separator of a fluid flow circuit. U.S. Pat. No. 5,194,145 describes an exemplary spinning membrane separator drive unit that would be suitable for incorporation into the blood separation device 10, but it should be understood that the spinning membrane separator drive unit 14 may be differently configured without departing from the scope of the present disclosure. The fluid flow circuit 12 of FIG. 2 does not employ a spinning membrane separator, so the spinning membrane separator drive unit 14 is not described in detail herein.

B. Centrifugal Separator

As for the centrifugal separator 16, it includes a centrifuge compartment 32 that may receive the other components of the centrifugal separator 16 (FIG. 3). The centrifuge compartment 32 may include a lid 34 that is opened to insert and remove a centrifugal separation chamber 36 of the fluid flow circuit 12. During a separation procedure, the lid 34 may be closed with the centrifugal separation chamber 36 positioned within the centrifuge compartment 32, as the centrifugal separation chamber 36 is spun or rotated about an axis 38 under the power of an electric drive motor or rotor 40 of the centrifugal separator 16.

The particular configuration and operation of the centrifugal separator 16 depends upon the particular configuration of the centrifugal separation chamber 36 of the fluid flow circuit 12. In one embodiment, the centrifugal separator 16 is similar in structure and operation to that of the ALYX system manufactured by Fenwal, Inc. of Lake Zurich, Ill., which is an affiliate of Fresenius Kabi AG of Bad Homburg, Germany, as described in greater detail in U.S. Pat. No. 8,075,468, which is incorporated herein by reference. More particularly, the centrifugal separator 16 may include a carriage or support 42 that holds the centrifugal separation chamber 36 and a yoke member 44. The yoke member 44 engages an umbilicus 46 of the fluid flow circuit 12, which extends between the centrifugal separation chamber 36 and a cassette 48 of the fluid flow circuit 12 (FIG. 4). The yoke member 44 causes the umbilicus 46 to orbit around the centrifugal separation chamber 36 at a one omega rotational speed. The umbilicus 46 twists about its own axis as it orbits around the centrifugal separation chamber 36. The twisting of the umbilicus 46 about its axis as it rotates at one omega with the yoke member 44 imparts a two omega rotation to the centrifugal separation chamber 36, according to known design. The relative rotation of the yoke member 44 at a one omega rotational speed and the centrifugal separation chamber 36 at a two omega rotational speed keeps the umbilicus 46 untwisted, avoiding the need for rotating seals.

Blood is introduced into the centrifugal separation chamber 36 by the umbilicus 46, with the blood being separated (e.g., into a layer of less dense components, such as platelet-rich plasma, and a layer of more dense components, such as packed red blood cells) within the centrifugal separation chamber 36 as a result of centrifugal forces as it rotates. Components of an interface monitoring system may be positioned within the centrifuge compartment 32 to oversee separation of blood within the centrifugal separation chamber 36. As shown in FIGS. 5-7, the interface monitoring system may include a light source 50 and a light detector 52, which is positioned and oriented to receive at least a portion of the light emitted by the light source 50. Preferably, the light source 50 and the light detector 52 are positioned on stationary surfaces of the centrifuge compartment 32, but it is also within the scope of the present disclosure for one or both to be mounted to a movable component of the centrifugal separator 16 (e.g., to the yoke member 44, which rotates at a one omega speed).

The orientation of the various components of the interface monitoring system depends at least in part on the particular configuration of the centrifugal separation chamber 36, which will be described in greater detail herein. In general, though, the light source 50 emits a light beam (e.g., a laser light beam) through the separated blood components within the centrifugal separation chamber 36 (which may be formed of a material that substantially transmits the light or at least a particular wavelength of the light without absorbing it). A portion of the light reaches the light detector 52, which transmits a signal to the controller 18 that is indicative of the location of an interface between the separated blood components. If the controller 18 determines that the interface is in the wrong location (which can affect the separation efficiency of the centrifugal separator 16 and/or the quality of the separated blood components), then it can issue commands to the appropriate components of the blood separation device 10 to modify their operation so as to move the interface to the proper location.

C. Other Components of the Blood Separation Device

In addition to the spinning membrane separator drive unit 14 and the centrifugal separator 16, the blood separation device 10 may include other components compactly arranged to aid blood processing.

The generally horizontal portion 22 of the case 20 of the illustrated blood separation device 10 includes a cassette station 54, which accommodates a cassette 48 of the fluid flow circuit 12 (FIG. 4). In one embodiment, the cassette station 54 is similarly configured to the cassette station of U.S. Pat. No. 5,868,696 (which is incorporated herein by reference), but is adapted to include additional components and functionality. The illustrated cassette station 54 includes a plurality of clamps or valves V1-V9 (FIG. 1), which move between a plurality of positions (e.g., between a retracted or lowered position and an actuated or raised position) to selectively contact or otherwise interact with corresponding valve stations C1-C9 of the cassette 48 of the fluid flow circuit 12 (FIGS. 2 and 4). Depending on the configuration of the fluid flow circuit 12, its cassette 48 may not include a valve station C1-C9 for each valve V1-V9 of the cassette station 54, in which case fewer than all of the valves V1-V9 will be used in a separation procedure, as will be described.

In the actuated position, a valve V1-V9 engages the associated valve station C1-C9 to prevent fluid flow through that valve station C1-C9 (e.g., by closing one or more ports associated with the valve station C1-C9, thereby preventing fluid flow through that port or ports). In the retracted position, a valve V1-V9 is disengaged from the associated valve station C1-C9 (or less forcefully contacts the associated valve station C1-C9 than when in the actuated position) to allow fluid flow through that valve station C1-C9 (e.g., by opening one or more ports associated with the valve station C1-C9, thereby allowing fluid flow through that port or ports). Additional clamps or valves V10 and V11 may be positioned outside of the cassette station 52 to interact with portions or valve stations C10 and C11 (which may be lengths of tubing) of the fluid flow circuit 12 to selectively allow and prevent fluid flow therethrough. The valves V1-V9 and corresponding valve stations C1-C9 of the cassette station 54 and cassette 48 may be differently configured and operate differently from the valves V10 and V11 and valve stations C10 and C11 that are spaced away from the cassette station 54.

The cassette station 54 may be provided with additional components, such as pressure sensors A1-A4, which interact with sensor stations S1-S4 of the cassette 48 to monitor the pressure at various locations of the fluid flow circuit 12. For example, if the blood source is a human donor, one or more of the pressure sensors A1-A4 may be configured to monitor the pressure of the donor's vein during blood draw and return. Other pressure sensors A1-A4 may monitor the pressure of a spinning membrane separator (if provided) and the centrifugal separation chamber 36. The controller 18 may receive signals from the pressure sensor A1-A4 that are indicative of the pressure within the fluid flow circuit 12 and, if a signal indicates a low- or high-pressure condition, the controller 18 may initiate an alarm or error condition to alert an operator to the condition and/or to attempt to bring the pressure to an acceptable level without operator intervention.

The blood separation device 10 may also include a plurality of pumps P1-P6 to cause fluid to flow through the fluid flow circuit 12. The pumps P1-P6 may be differently or similarly configured and/or function similarly or differently from each other. In the illustrated embodiment, the pumps P1-P6 are configured as peristaltic pumps, which may be generally configured as described in U.S. Pat. No. 5,868,696. Each pump P1-P6 engages a different tubing loop T1-T6 extending from a side surface of the cassette 48 (FIG. 4) and may be selectively operated under command of the controller 18 to cause fluid to flow through a portion of the fluid flow circuit 12, as will be described in greater detail. In one embodiment, all or a portion of the cassette station 54 may be capable of translational motion in and out of the case 20 to allow for automatic loading of the tubing loops T1-T6 into the associated pump P1-P6.

The illustrated blood separation device 10 also includes a centrifugal separator sensor M1 for determining one or more properties of fluids flowing out of and/or into the centrifugal separator 16. If the fluid flowing out of the centrifugal separator 16 includes red blood cells, the centrifugal separator sensor M1 may be configured to determine the hematocrit of the fluid. If the fluid flowing out of the centrifugal separator 16 is platelet-rich plasma, the centrifugal separator sensor M1 may be configured to determine the platelet concentration of the platelet-rich plasma. The centrifugal separator sensor M1 may detect the one or more properties of a fluid by optically monitoring the fluid as it flows through tubing of the fluid flow circuit 12 or by any other suitable approach. The controller 18 may receive signals from the centrifugal separator sensor M1 that are indicative of the one or more properties of fluid flowing out of the centrifugal separator 16 and use the signals to optimize the separation procedure based upon that property or properties. If the property or properties is/are outside of an acceptable range, then the controller 18 may initiate an alarm or error condition to alert an operator to the condition. A suitable device and method for monitoring hematocrit and/or platelet concentration is described in U.S. Pat. No. 6,419,822 (which is incorporated herein by reference), but it should be understood that a different approach may also be employed for monitoring hematocrit and/or platelet concentration of fluid flowing out of the centrifugal separator 16.

The illustrated blood separation device 10 further includes a spinner outlet sensor M2, which accommodates tubing of a fluid flow circuit that flows a separated blood component out of a spinning membrane separator of the fluid flow circuit. The fluid flow circuit 12 of FIG. 2 does not employ a spinning membrane separator, so the spinner outlet sensor M2 is not described in detail herein.

The illustrated blood separation device 10 also includes an air detector M3 (e.g., an ultrasonic bubble detector), which accommodates tubing of the fluid flow circuit 12 that flows fluid to a recipient. It may be advantageous to prevent air from reaching the recipient, so the air detector M3 may transmit signals to the controller 18 that are indicative of the presence or absence of air in the tubing. If the signal is indicative of air being present in the tubing, the controller 18 may initiate an alarm or error condition to alert an operator to the condition and/or to take corrective action to prevent the air from reaching the recipient (e.g., by reversing the flow of fluid through the tubing or diverting flow to a vent location).

The generally vertical portion 24 of the case 18 may include a plurality of weight scales W1-W6 (six are shown, but more or fewer may be provided), each of which may support one or more fluid containers F1-F5 of the fluid flow circuit 12 (FIG. 2). The containers F1-F5 receive blood components separated during processing or intravenous fluids or additive fluids. Each weight scale W1-W6 transmits to the controller 18 a signal that is indicative of the weight of the fluid within the associated container F1-F5 to track the change of weight during the course of a procedure. This allows the controller 18 to process the incremental weight changes to derive fluid processing volumes and flow rates and subsequently generate signals to control processing events based, at least in part, upon the derived processing volumes. For example, the controller 18 may diagnose leaks and obstructions in the fluid flow circuit 12 and alert an operator.

The illustrated case 20 is also provided with a plurality of hooks or supports H1 and H2 that may support various components of the fluid flow circuit 12 or other suitably sized and configured objects.

D. Controller

According to an aspect of the present disclosure, the blood separation device 10 includes a controller 18, which is suitably configured and/or programmed to control operation of the blood separation device 10. In one embodiment, the controller 18 comprises a main processing unit (MPU), which can comprise, e.g., a Pentium™ type microprocessor made by Intel Corporation, although other types of conventional microprocessors can be used. In one embodiment, the controller 18 may be mounted inside the generally vertical portion 24 of the case 20, adjacent to or incorporated into an operator interface station (e.g., a touchscreen). In other embodiments, the controller 18 and operator interface station may be associated with the generally horizontal portion 22 or may be incorporated into a separate device that is connected (either physically, by a cable or the like, or wirelessly) to the blood separation device 10.

The controller 18 is configured and/or programmed to execute at least one blood processing application but, more advantageously, is configured and/or programmed to execute a variety of different blood processing applications. For example, the controller 18 may be configured and/or programmed to carry out one or more of the following: a double unit red blood cell collection procedure, a plasma collection procedure, a plasma/red blood cell collection procedure, a red blood cell/platelet/plasma collection procedure, a platelet collection procedure, a platelet/plasma collection procedure, and (as will be described in detail herein) an MNC collection procedure. Additional or alternative procedure applications can be included without departing from the scope of the present disclosure.

More particularly, in carrying out any one of these blood processing applications, the controller 18 is configured and/or programmed to control one or more of the following tasks: drawing blood into a fluid flow circuit 12 mounted to the blood separation device 10, conveying blood through the fluid flow circuit 12 to a location for separation (i.e., into a spinning membrane separator or the centrifugal separation chamber 36 of the fluid flow circuit 12), separating the blood into two or more components as desired, and conveying the separated components into storage containers, to a second location for further separation (e.g., into whichever of the spinning membrane separator and centrifugal separation chamber 36 that was not used in the initial separation stage), or to a recipient (which may be the source from which the blood was originally drawn).

This may include instructing the spinning membrane separator drive unit 14 and/or the centrifugal separator 16 to operate at a particular rotational speed and instructing a pump P1-P6 to convey fluid through a portion of the fluid flow circuit 12 at a particular flow rate. Hence, while it may be described herein that a particular component of the blood separation device 10 (e.g., the spinning membrane separator drive unit 14 or the centrifugal separator 16) performs a particular function, it should be understood that that component is being controlled by the controller 18 to perform that function.

For procedures that call for the use of both the centrifugal separator 16 and the spinning membrane separator drive unit 14, a properly programmed controller 18 is especially important to coordinate the operation of these two components, along with the other components of the blood separation device 10 to ensure that flow to and from the centrifugal separator 16 and spinning membrane separator drive unit 14 is at the proper level and that the components are functioning properly to process the blood circulating through the fluid flow circuit 12.

Before, during, and after a procedure, the controller 18 may receive signals from various components of the blood separation device 10 (e.g., the pressure sensors A1-A4) to monitor various aspects of the operation of the blood separation device 10 and characteristics of the blood and separated blood components as they flow through the fluid flow circuit 12. If the operation of any of the components and/or one or more characteristics of the blood or separated blood components is outside of an acceptable range, then the controller 18 may initiate an alarm or error condition to alert the operator and/or take action to attempt to correct the condition. The appropriate corrective action will depend upon the particular error condition and may include action that is carried out with or without the involvement of an operator.

For example, the controller 18 may include an interface control module, which receives signals from the light detector 52 of the interface monitoring system. The signals that the controller 18 receives from the light detector 52 are indicative of the location of an interface between the separated blood components within the centrifugal separation chamber 36. If the controller 18 determines that the interface is in the wrong location, then it can issue commands to the appropriate components of the blood separation device 10 to modify their operation so as to move the interface to the proper location. For example, the controller 18 may instruct one of the pumps P1-P6 to cause blood to flow into the centrifugal separation chamber 36 at a different rate and/or for a separated blood component to be removed from the centrifugal separation chamber 36 at a different rate and/or for the centrifugal separation chamber 36 to be spun at a different speed by the centrifugal separator 16. A particular protocol carried out by the interface control module in adjusting the position of the interface within the centrifugal separation chamber 36 will be described in greater detail with respect to an exemplary centrifugal separation chamber 36.

If provided, an operator interface station associated with the controller 18 allows the operator to view on a screen or display (in alpha-numeric format and/or as graphical images) information regarding the operation of the system. The operator interface station also allows the operator to select applications to be executed by the controller 18, as well as to change certain functions and performance criteria of the system. If configured as a touchscreen, the screen of the operator interface station can receive input from an operator via touch-activation. Otherwise, if the screen is not a touchscreen, then the operator interface station may receive input from an operator via a separate input device, such as a computer mouse or keyboard. It is also within the scope of the present disclosure for the operator interface station to receive input from both a touchscreen and a separate input device, such as a keypad.

II. The Disposable Fluid Flow Circuit A. Overview

As for the fluid flow circuit or flow set 12 (FIG. 2), it is intended to be a sterile, single use, disposable item. Before beginning a given blood processing and collection procedure, the operator loads various components of the fluid flow circuit 12 in the case 20 in association with the blood separation device 10. The controller 18 implements the procedure based upon preset protocols, taking into account other input from the operator. Upon completing the procedure, the operator removes the fluid flow circuit 12 from association with the blood separation device 10. The portions of the fluid flow circuit 12 holding the collected blood component or components (e.g., collection containers or bags) are removed from the case 20 and retained for storage, transfusion, or further processing. The remainder of the fluid flow circuit 12 is removed from the case 20 and discarded.

A variety of different disposable fluid flow circuits may be used in combination with the blood separation device 10, with the appropriate fluid flow circuit depending on the separation procedure to be carried out using the system. Generally speaking, though, the fluid flow circuit 12 includes a cassette 48 (FIG. 4), to which the other components of the fluid flow circuit 12 are connected by flexible tubing. The other components may include a plurality of fluid containers F1-F5 (for holding blood, a separated blood component, an intravenous fluid, or an additive solution, for example), one or more blood source access devices (e.g., a connector for accessing blood within a fluid container), and a spinning membrane separator (not illustrated) and/or a centrifugal separation chamber 36 (FIGS. 8-15).

B. Cassette and Tubing

The cassette 48 (FIG. 4) provides a centralized, programmable, integrated platform for all the pumping and many of the valving functions required for a given blood processing procedure. In one embodiment, the cassette 48 is similarly configured to the cassette of U.S. Pat. No. 5,868,696, but is adapted to include additional components (e.g., more tubing loops T1-T6) and functionality.

In use, the cassette 48 is mounted to the cassette station 54 of the blood separation device 10, with a flexible diaphragm of the cassette 48 placed into contact with the cassette station 54. The flexible diaphragm overlays an array of interior cavities formed by the body of the cassette 48. The different interior cavities define sensor stations S1-S4, valve stations C1-C9, and a plurality of flow paths. The side of the cassette 48 opposite the flexible diaphragm may be sealed by another flexible diaphragm or a rigid cover, thereby sealing fluid flow through the cassette 48 from the outside environment.

Each sensor station S1-S4 is aligned with an associated pressure sensor A1-A4 of the cassette station 54, with each pressure sensor A1-A4 capable of monitoring the pressure within the associated sensor station S1-S4. Each valve station C1-C9 is aligned with an associated valve V1-V9, and may define one or more ports that allow fluid communication between the valve station C1-C9 and another interior cavity of the cassette 48 (e.g., a flow path). As described above, each valve V1-V9 is movable under command of the controller 18 to move between a plurality of positions (e.g., between a retracted or lowered position and an actuated or raised position) to selectively contact the valve stations C1-C9 of the cassette 48. In the actuated position, a valve V1-V9 engages the associated valve station C1-C9 to close one or more of its ports to prevent fluid flow therethrough. In the retracted position, a valve V1-V9 is disengaged from the associated valve station C1-C9 (or less forcefully contacts the associated valve station C1-C9 than when in the actuated position) to open one or more ports associated with the valve station C1-C9, thereby allowing fluid flow therethrough.

As described, a plurality of tubing loops T1-T6 extend from the side surface of the cassette 48 to interact with pumps P1-P6 of the blood separation device 10. In the illustrated embodiment, six tubing loops T1-T6 extend from the cassette 48 to be received by a different one of six pumps P1-P6, but in other embodiments, a procedure may not require use of all of the pumps P1-P6, in which case the cassette 48 may include fewer than six tubing loops. The different pumps P1-P6 may interact with the tubing loops T1-T6 of the cassette 48 to perform different tasks during a separation procedure (as will be described in greater detail), but in one embodiment, a different one of the pumps P1-P6 may be configured to serve as an anticoagulant pump P1, a source pump P2, a recirculation pump P3, a spinner pump P4, a plasma pump P5, and an additive pump P6. As will be described, certain procedures require fewer than all of the sensor stations, valve stations, and/or tubing loops illustrated in the exemplary cassette 48 of FIG. 4, such that it should be understood that the cassettes of different fluid flow circuits 12 may be differently configured (e.g., with fewer sensor stations, valve stations, and/or tubing loops) without departing from the scope of the present disclosure.

Additional tubing extends from the side surface of the cassette 48 to connect to the other components of the fluid flow circuit 12, such as the various fluid containers F1-F5, the spinning membrane separator (if provided), and the centrifugal separation chamber 36 (if provided). The number and content of the various fluid containers F1-F5 depends upon the procedure for which the fluid flow circuit 12 is used, with the fluid containers F1-F5 of one particular fluid flow circuit 12 and procedure being described in greater detail herein. If the fluid flow circuit 12 includes a centrifugal separation chamber 36, then the tubing connected to it (which includes one inlet tube and two outlet tubes) may be aggregated into an umbilicus 46 (FIG. 3) that is engaged by the yoke member 44 of the centrifugal separator 16 (as described above) to cause the umbilicus 46 to orbit around and spin or rotate the centrifugal separation chamber 36 during a separation procedure.

Various additional components may be incorporated into the tubing leading out of the cassette 48 or into one of the cavities of the cassette 48. For example, as shown in FIG. 2, a manual clamp 56 may be associated with a line or lines leading to the blood source and/or fluid recipient, a return line filter 58 (e.g., a microaggregate filter) may be associated with a line leading to a fluid recipient, filters (not illustrated) may be positioned upstream of one or more of the fluid containers to remove a substance (e.g., leukocytes) from a separated component (e.g., red blood cells or platelets) flowing into the fluid container, and/or an air trap 62 may be positioned on a line upstream of the centrifugal separation chamber 36.

C. Centrifugal Separation Chamber

A fluid flow circuit 12 may be provided with a centrifugal separation chamber 36 if platelets, white blood cells, and/or (as described herein) MNCs are to be separated and collected. An exemplary centrifugal separation chamber 36 a is shown in FIGS. 8 and 9, while FIG. 10 illustrates the fluid flow path defined by the centrifugal separation chamber 36 a. In the illustrated embodiment, the body of the centrifugal separation chamber 36 a is pre-formed in a desired shape and configuration (e.g., by injection molding) from a rigid, biocompatible plastic material, such as a non-plasticized medical grade acrylonitrile-butadiene-styrene (ABS). All contours, ports, channels, and walls that affect the blood separation process are preformed in a single, injection molded operation. Alternatively, the centrifugal separation chamber 36 a can be formed by separate molded parts, either by nesting cup-shaped subassemblies or two symmetric halves.

The underside of the centrifugal separation chamber 36 a includes a shaped receptacle 86 that is suitable for receiving an end of the umbilicus 46 of the fluid flow circuit 12 (FIG. 3). A suitable receptacle 86 and the manner in which the umbilicus 46 may cooperate with the receptacle 86 to deliver fluid to and remove fluid from the centrifugal separation chamber 36 a are described in greater detail in U.S. Pat. No. 8,075,468.

The illustrated centrifugal separation chamber 36 a has radially spaced apart inner (low-g) and outer (high-g) side wall portions 88 and 90, a bottom or first end wall portion 92, and a cover or second end wall portion 93. The cover 93 comprises a simple flat part that can be easily welded or otherwise secured to the body of the centrifugal separation chamber 36 a. Because all features that affect the separation process are incorporated into one injection molded component, any tolerance differences between the cover 93 and the body of the centrifugal separation chamber 36 a will not affect the separation efficiencies of the centrifugal separation chamber 36 a. The wall portions 88 and 90, the bottom 92, and the cover 93 together define an enclosed, generally annular channel 94 (FIG. 10).

The (whole blood) inlet 96 communicating with the channel 94 is defined between opposing interior radial walls 98 and 100. One of the interior walls 98 joins the outer (high-g) wall portion 90 and separates the upstream and downstream ends of the channel 94. The interior walls 98 and 100 define the inlet passageway 96 of the centrifugal separation chamber 36 a which, in one flow configuration, allows fluid to flow from the umbilicus 46 to the upstream end of the channel 94.

The illustrated centrifugal separation chamber 36 a further includes first and second outlets 102 and 104, respectively, which may be defined by opposing surfaces of interior radial walls. Both the first and second outlets 102 and 104 extend radially inward from the channel 94. The first (plasma) outlet 102 extends radially inward from an opening which, in the illustrated embodiment, is located at the inner side wall portion 88, while the second (red blood cell) outlet 104 extends radially inward from an opening that is associated with the outer side wall portion 90. The illustrated first outlet 102 is positioned adjacent to the inlet 96 (near the upstream end of the channel 94), while the second outlet 104 may be positioned at the opposite, downstream end of the channel 94.

It should be understood that the centrifugal separation chamber 36 a illustrated in FIG. 8 is merely exemplary and that the centrifugal separation chamber 36 may be differently configured without departing from the scope of the present disclosure. For example, FIGS. 11 and 12 show an alternative embodiment of a centrifugal separation chamber 36 b, while FIG. 13 illustrates the fluid flow path defined by the centrifugal separation chamber 36 b. The centrifugal separation chamber 36 b is similar to the centrifugal separation chamber 36 a except for the location at which the inlet 96 opens into the channel 94. In the centrifugal separation chamber 36 a of FIG. 8, the inlet 96 opens into the channel 94 adjacent to the first end wall portion 92 (while the outlets 102 and 104 open into the channel 94 adjacent to the second end wall portion 93), as best shown in FIGS. 9 and 10. In contrast, the inlet 96 of the centrifugal separation chamber 36 b of FIG. 11 opens into the channel 94 adjacent to the second end wall portion 93 (along with the outlets 102 and 104), as best shown in FIGS. 12 and 13. The location at which the inlet 96 opens into the channel 94 may affect the separation of fluid within the channel 94, so the centrifugal separation chamber 36 a of FIG. 8 may be preferable for certain procedures or for use in combination with certain blood separation devices, while the centrifugal separation chamber 36 b of FIG. 11 may be preferable for other procedures or for use in combination with other blood separation devices.

FIGS. 14 and 15 show another exemplary embodiment of a centrifugal separation chamber 36 c suitable for incorporation into a fluid flow circuit 12. The centrifugal separation chamber 36 c is similar to the centrifugal separation chambers 36 a and 36 b of FIGS. 8 and 11 except for the location at which the inlet 96 opens into the channel 94. In contrast to the inlets 96 of the centrifugal separation chambers 36 a and 36 b of FIGS. 8 and 11, the inlet 96 of the centrifugal separation chamber 36 c of FIG. 14 opens into the channel 94 at an intermediate axial location that is spaced from the first and second end wall portion 92 and 93 (while the outlets 102 and 104 open into the channel adjacent to the second end wall portion 93), as best shown in FIG. 15. The inlet 96 may open into the channel 94 at a location that is closer to the first end wall portion 92 than to the second end wall portion 93, at a location that is closer to the second end wall portion 93 than to the first end wall portion 92, or at a location that is equally spaced between the first and second end wall portions 92 and 93. The axial location at which the inlet 96 opens into the channel 94 may affect the separation of fluid within the channel 94, so the preferred location at which the inlet 96 opens into the channel 94 (which may also depend upon the nature of the blood separation device paired with the centrifugal separation chamber 36 c) may be experimentally determined.

1. Centrifugal Separation and Interface Detection Principles

Blood flowed into the channel 94 separates into an optically dense layer RBC and a less optically dense layer PLS (FIGS. 16-18) as the centrifugal separation chamber 36 is rotated about the rotational axis 38. The optically dense layer RBC forms as larger and/or heavier blood particles move under the influence of centrifugal force toward the outer (high-g) wall portion 90. The optically dense layer RBC will typically include red blood cells (and, hence, may be referred to herein as the “RBC layer”) but, depending on the speed at which the centrifugal separation chamber 36 is rotated, other cellular components (e.g., larger white blood cells) may also be present in the optically dense layer RBC.

The less optically dense layer PLS typically includes a plasma constituent, such as platelet-rich plasma or platelet-poor plasma (and, hence, will be referred to herein as the “PLS layer”). Depending on the speed at which the centrifugal separation chamber 36 is rotated and the length of time that the blood is resident therein, other components (e.g., smaller white blood cells and anticoagulant) may also be present in the less optically dense layer PLS.

In one embodiment, blood introduced into the channel 94 via the inlet 96 will travel in a generally clockwise direction (in the orientation of FIG. 8) as the optically dense layer RBC separates from the less optically dense layer PLS. The optically dense layer RBC continues moving in the clockwise direction as it travels the length of the channel 94 along the outer side wall portion 90, from the upstream end to the downstream end, where it exits the channel 94 via the second outlet 104. The less optically dense layer PLS separated from the optically dense layer RBC reverses direction, moving counterclockwise along the inner side wall portion 88 to the first outlet 102, adjacent to the inlet 96. The inner side wall portion 88 may be tapered inward as it approaches the second outlet 104 to force the plasma liberated at or adjacent to the downstream end of the channel 94 to drag the interface back towards the upstream end of the channel 94, where the lower surface hematocrit will re-suspend any platelets settled on the interface.

As described above, the transition between the optically dense layer RBC and the less optically dense layer PLS may be referred to as the interface INT. In one embodiment, the interface INT contains mononuclear cells and peripheral blood stem cells. The location of the interface INT within the channel 94 of the centrifugal separation chamber 36 can dynamically shift during blood processing, as FIGS. 16-18 show. If the location of the interface INT is too high (that is, if it is too close to the inner side wall portion 88 and the first outlet 102, as in FIG. 17), red blood cells can flow into the first outlet 102, potentially adversely affecting the quality of the low density components (platelet-rich plasma or platelet-poor plasma). On the other hand, if the location of the interface INT is too low (that is, if it resides too far away from the inner wall portion 88, as FIG. 18 shows), the collection efficiency of the system may be impaired. The ideal or target interface INT may be experimentally determined, which may vary depending on any of a number of factors (e.g., the configuration of the centrifugal separation chamber 36, the rate at which the centrifugal separation chamber 36 is rotated about the rotational axis 38, etc.). As will be described herein, it may be advantageous to temporarily move the interface INT away from the location of FIG. 16 during a separation procedure.

As described above, the blood separation device 10 may include an interface monitoring system and a controller 18 with an interface control module to monitor and, as necessary, correct the position of the interface INT. In one embodiment, the centrifugal separation chamber 36 is formed with a ramp 106 extending from the high-g wall portion 90 at an angle α across at least a portion of the channel 94 (FIGS. 8 and 16-18). The angle α, measured with respect to the rotational axis 38 is about 25° in one embodiment. FIGS. 16-18 show the orientation of the ramp 106 when viewed from the low-g side wall portion 88 of the centrifugal separation chamber 36. Although it describes a flexible separation chamber, the general structure and function of the ramp 106 may be better understood with reference to U.S. Pat. No. 5,632,893, which is incorporated herein by reference. The ramp 106 may be positioned at any of a number of locations between the upstream and downstream ends of the channel 94, but in one embodiment, the ramp 106 may be positioned generally adjacent to the first outlet 102, in the path of fluid and/or a fluid component moving from the inlet 96 to the first outlet 102.

The ramp 106 makes the interface INT between the optically dense layer RBC and the less optically dense layer PLS more discernible for detection, displaying the optically dense layer RBC, less optically dense layer PLS, and interface INT for viewing through a light-transmissive portion of the centrifugal separation chamber 36. To that end, the ramp 106 and at least the portion of the centrifugal separation chamber 36 angularly aligned with the ramp 106 may be formed of a light-transmissive material, although it may be advantageous for the entire centrifugal separation chamber 36 to be formed of the same light-transmissive material.

In the illustrated embodiment, the light source 50 of the interface monitoring system is secured to a fixture or wall of the centrifuge compartment 32 and oriented to emit a light that is directed toward the rotational axis 38 of the centrifugal separator 16, as shown in FIGS. 5-7. If the light detector 52 is positioned at an angle with respect to the light source 50 (as in the illustrated embodiment), the light L emitted by the light source 50 must be redirected from its initial path before it will reach the light detector 52. In the illustrated embodiment, the light L is redirected by a reflector that is associated with a light-transmissive portion of the inner side wall portion 88, as shown in FIGS. 5 and 6. The reflector may be a separate piece that is secured to the inner side wall portion 88 (e.g., by being bonded thereto) or may be integrally formed with the body of the centrifugal separation chamber 36.

In one embodiment, the reflector may be a reflective surface, such as a mirror, that is oriented (e.g., at a 45° angle) to direct light L emitted by the light source 50 to the light detector 52. In another embodiment, the reflector is provided as a prismatic reflector 108 (FIGS. 7, 19, and 20), which is formed of a light-transmissive material (e.g., a clear plastic material) and has inner and outer walls 110 and 112 and first and second end walls 114 and 116 (FIG. 19). The inner wall 110 is positioned against the inner side wall portion 88 of the centrifugal separation chamber 36 and is oriented substantially perpendicular to the initial path of the light L from the light source 50. This allows light L from the light source 50 to enter into the prismatic reflector 108 via the inner wall 110 while continuing along its initial path. The light L continues through the prismatic reflector 108 along its initial path until it encounters the first end wall 114. The first end wall 114 is oriented at an angle (e.g., an approximately 45° angle) with respect to the first surface 110 and the second end wall 116, causing the light to be redirected within the prismatic reflector 108, rather than exiting the prismatic reflector 108 via the first end wall 114.

The first end wall 114 directs the light L at an angle to its initial path (which may be an approximately 90° angle, directing it from a path toward the rotational axis 38 to a path that is generally parallel to the rotational axis 38) toward the second end wall 116 (FIG. 20). The first end wall 114 and the inner and outer walls 110 and 112 of the prismatic reflector 108 may be configured to transmit the redirected light L from the first end wall 114 to the second end wall 116 by total internal reflection. The second end wall 116 is oriented substantially perpendicular to the redirected path of the light L through the prismatic reflector 108, such that the light L will exit the prismatic reflector 108 via the second end wall 116, continuing along its redirected path. In one embodiment, the second end wall 116 is roughened or textured or otherwise treated or conditioned to diffuse the light L as it exits the prismatic reflector 108, which may better ensure that the light L reaches the light detector 52 (FIG. 7).

The prismatic reflector 108 may be angularly aligned with the ramp 106, such that the light L from the light source 50 will only enter into the prismatic reflector 108 when the ramp 106 has been rotated into the path of the light L. At all other times (when the ramp 106 is not in the path of the light L), the light L will not reach the prismatic reflector 108 and, thus, will not reach the light detector 52. This is illustrated in FIGS. 21-24, which show the ramp 106 and prismatic reflector 108 as the centrifugal separation chamber 36 is rotated about the rotational axis 38 (while the light source 50 remains in a fixed location). In FIG. 21, the ramp 106 and prismatic reflector 108 have not yet been rotated into the initial path of the light L from the light source 50. At this time, no light is transmitted to the light detector 52, such that the output voltage of the light detector 52 (i.e., the signal transmitted from the light detector 52 to the controller 18) is in a low- or zero-state (FIG. 25).

Upon the ramp 106 first being rotated into the initial path of the light L from the light source 50 (FIG. 22), the light L will begin to reach the prismatic reflector 108, which directs the light L to the light detector 52. This causes the voltage output of the light detector 52 (i.e., the signal transmitted from the light detector 52 to the controller 18) to increase to a non-zero value or state, as shown in FIG. 26.

During a calibration phase, the channel 94 is filled with a fluid that will transmit the light L rather than absorbing or reflecting the light or otherwise preventing the light L from reaching the prismatic reflector 108, such that the voltage output of the light detector 52 will remain generally constant as the ramp 106 and prismatic reflector 108 are rotated through the initial path of the light L from the light source 50 (FIGS. 23 and 27). Such a calibration phase may coincide with a priming phase during which saline is pumped through the fluid flow circuit 12 to prime the fluid flow circuit 12 or may comprise a separate phase. A calibration phase may be useful in ensuring the proper operation of the light source 50 and the light detector 52, standardizing the readings taken during a separation procedure in case of any irregularities or imperfections of the centrifugal separation chamber 36, and establishing a baseline value for the signal transmitted from the light detector 52 to the controller 18 when the ramp 106 and prismatic reflector 108 are aligned with the light source 50. As will be described in greater detail, the voltage output of the light detector 52 will typically not remain constant as the ramp 106 and prismatic reflector 108 are rotated through the initial path of the light L from the light source 50 because the different fluid layers displayed on the ramp 106 will allow different amounts of light L to reach the prismatic reflector 108.

The ramp 106 and prismatic reflector 108 are eventually rotated out of alignment with the light source 50 (FIG. 24), at which time no light L will reach the prismatic reflector 108 and the voltage output of the light detector 52 will return to its low- or zero-state (FIG. 28).

It may be advantageous for the light L to have a relatively small diameter for improved resolution of the signal that is generated by the light detector 52.

2. Exemplary Interface Detection and Correction Procedure

During separation of blood within the channel 94, the light L from the light source 50 travels through a light-transmissive portion of the outer side wall portion 90 and the ramp 106 to intersect the separated blood components thereon when the ramp 106 has been rotated into the initial path of the light L. After passing through the ramp 106, the light continues through the channel 94 and the fluids in the channel 94. At least a portion of the light L (i.e., the portion not absorbed or reflected by the fluids) exits the channel 94 by striking and entering a light-transmissive portion of the inner side wall portion 88. The light L passes through the inner side wall portion 88 and enters the prismatic reflector 108, which redirects the light L from its initial path to the light detector 50, as described above. Thus, it will be seen that the light L reaches the light detector 52 after intersecting and traveling through the separated blood components in the channel 94 only once, in contrast to known systems in which light from a light source travels through a ramp and a fluid-filled channel before being reflected back through the channel to reach a light detector. Requiring the light L to traverse the fluid-filled channel 94 only once before reaching the light detector 52 instead of twice may be advantageous in that it tends to increase the intensity of the light L that reaches the light detector 52, which may improve monitoring and correction of the interface location.

The light detector 52 generates a signal that is transmitted to the interface control module of the controller 18, which can determine the location of the interface INT on the ramp 106. In one embodiment, the location of the interface INT is associated with a change in the amount of light L that is transmitted through the less optically dense layer PLS and the optically dense layer RBC. For example, the light source 50 may be configured to emit a light L that is more readily transmitted by platelet-rich plasma or platelet-poor plasma than by red blood cells, such as red visible light (from a laser or a differently configured light source 50), which is substantially absorbed by red blood cells. The less optically dense layer PLS and the optically dense layer RBC each occupy a certain portion of the ramp 106, with the light detector 52 receiving different amounts of light L depending on whether the light L travels through the less optically dense layer PLS on the ramp 106 or the optically dense layer RBC on the ramp 106. The percentage of the ramp 106 occupied by each layer is related to the location of the interface INT in the channel 94. Thus, by measuring the amount of time that the voltage output or signal from the light detector 52 is relatively high (corresponding to the time during which the light L is passing through only the less optically dense layer PLS on the ramp 106), the controller 18 may determine the location of the interface INT and take steps to correct the location of the interface INT, if necessary.

FIGS. 29-32 show a portion of the ramp 106 being rotated into and through the initial path of the light L from the light source 50. Four specific events are shown: just before the ramp 106 is rotated into the path of the light L (FIG. 29), the ramp 106 first being rotated into the path of the light L (FIG. 30), just before the interface INT displayed on the ramp 106 is rotated into the path of the light L (FIG. 31), and just after the interface INT is rotated into the path of the light L (FIG. 32). FIGS. 33-36 respectively illustrate the voltage output of the light detector 52 (corresponding to the signal that it transmits to the controller 18) during each of these events.

As described above, the light detector 52 will receive no light L from the light source 50 when the prismatic reflector 108 is out of alignment with the initial path of the light L from the light source 50, as shown in FIG. 29. FIG. 33 shows that the output voltage of the light detector 52 (i.e., the signal transmitted from the light detector 52) to the controller 18) at this time is in a low- or zero-state.

When the ramp 106 is first rotated into the path of light L from the light source 50 (FIG. 30), the light detector 52 may begin receiving light L. The amount of light L received by the light detector 52 depends upon the fluid on the ramp 106 encountered by the light L (i.e., the fluid in the channel 94 between the ramp 106 and the inner side wall portion 88 that the light L must traverse before being directed to the light detector 52). As described above, the less optically dense layer PLS occupies a certain percentage of the channel 94 adjacent to the inner side wall portion 88, while the optically dense layer RBC occupies a certain percentage of the channel 94 adjacent to the outer side wall portion 90 (with the interface INT positioned at the transition between the two separated blood component layers). The illustrated ramp 106 is closest to the inner side wall portion 88 at its left end (in the orientation of FIGS. 29-32), while being farther spaced from the inner side wall portion 88 at its right end. At and adjacent to its left end, the ramp 106 will display only the fluid positioned closest to the inner side wall portion 88 (i.e., the less optically dense layer PLS), while the ramp 106 will display only the fluid positioned closest to the outer side wall portion 90 (i.e., the optically dense layer RBC) at and adjacent to its right end, as shown in FIGS. 29-32. At some point between its ends, the angled ramp 106 will be at a radial position where it will display the transition between the less optically dense layer PLS and the optically dense layer RBC (i.e., the interface INT). Hence, the location of the interface INT on the ramp 106 is dependent upon the percentage of the width of the ramp 106 that displays the less optically dense layer PLS (which is indicative of the percentage of the channel 94 occupied by the less optically dense layer PLS) and the percentage of the width of the ramp 106 that displays the optically dense layer RBC (which is indicative of the percentage of the channel 94 occupied by the optically dense layer RBC). It should be understood that the percentage of the ramp 106 occupied by the less optically dense layer PLS and by the optically dense layer RBC is not necessarily equal to the percentage of the channel 94 occupied by the less optically dense layer PLS and by the optically dense layer RBC, but that the percentage of the ramp 106 occupied by a separated blood component layer may be merely indicative of the percentage of the channel 94 occupied by that separated blood component layer.

In such an embodiment, as the ramp 106 is rotated into the path of the light L from the light source 50, the light L will first encounter the portion of the ramp 106 that is positioned closest to the inner side wall portion 88 (i.e., the section of the ramp 106 that most restricts the channel 94), as shown in FIG. 30. As described above, the less optically dense layer PLS will be positioned adjacent to the inner side wall portion 88 as it separates from the optically dense layer RBC, such that the fluid displayed on this radially innermost section of the ramp 106 (i.e., the fluid present in the channel 94 between the ramp 106 and the inner side wall portion 88) will be the less optically dense layer PLS. The light is substantially transmitted through the less optically dense layer PLS to the inner side wall portion 88, and through the light-transmissive inner side wall portion 88 to the prismatic reflector 108, which redirects the light L to the light detector 52. This causes the voltage output of the light detector 52 (i.e., the signal transmitted from the light detector 52 to the controller 18) to increase to a non-zero value or state, as shown in FIG. 34. Depending on the nature of the light L, the amount of light L received by the light detector 52 (and, hence, the magnitude of the voltage output) after the light L has passed through the less optically dense layer PLS may be greater than, less than, or equal to the amount of light L received by the light detector 52 after passing through saline during the calibration phase described above.

Further rotation of the ramp 106 through the path of light L from the light source 50 exposes the light L to portions of the ramp 106 that are increasingly spaced from the inner side wall portion 88 (i.e., the light L travels through portions of the channel 94 that are less restricted by the ramp 106 as the ramp 106 is rotated through the path of the light L). Up until the time that the interface INT on the ramp 106 is rotated into the path of the light L (as shown in FIG. 31), the only fluid in the channel 94 that the light L will have passed through will be the less optically dense layer PLS, such that a generally uniform level of light reaches the light detector 52 between the conditions shown in FIGS. 30 and 31. Accordingly, the voltage output of the light detector 52 will be generally uniform (at an elevated level) the whole time that the ramp 106 passes through the path of the light L before being exposed to the interface INT, as shown in FIG. 35. The controller 18 may be programmed and/or configured to consider a signal that deviates from a maximum signal level (e.g., a 10% decrease) to be part of the elevated signal for purposes of calculating the pulse width of the signal. The controller 18 will treat a greater deviation (i.e., a greater decrease in the magnitude of the signal) as the end of the elevated signal for purposes of calculating the pulse width of the signal.

Just after the interface INT has been rotated into the path of light L from the light source 50, the light L will begin to encounter the optically dense layer RBC in the channel 94, as shown in FIG. 32). As described above, the optically dense layer RBC will be positioned adjacent to the outer side wall portion 90 as it separates from the less optically dense layer PLS, such that the optically dense layer RBC will not be displayed on the ramp 106 until the ramp 106 is spaced a greater distance away from the inner side wall portion 88 (i.e., toward the right end of the ramp 106 in the orientation of FIGS. 29-32). Less light L is transmitted through the optically dense layer RBC than through the less optically dense layer PLS (which may include all or substantially all of the light L being absorbed by the optically dense layer RBC), such that the amount of light L that reaches the light detector 52 will decrease compared to the amount of light L that reaches the light detector 52 while traveling through only the less optically dense layer PLS in the channel 94 (FIGS. 30 and 31).

When receiving less light L, the voltage output or signal from the light detector 52 will decrease to a lower level than when the light L was passing through only the less optically dense layer PLS in the channel 94, as shown in FIG. 36. When the light L encounters the optically dense layer RBC in the channel 94, the light detector 52 may be generating a signal or voltage output that is approximately equal to its zero-state (as in FIG. 33, when the light detector 52 is receiving no light L) or a signal or voltage output that is some degree less than the magnitude of the signal or voltage output generated while the light L encounters only the less optically dense layer PLS in the channel 94. The controller 18 may be programmed and/or configured to recognize this lower level signal as representing the presence of the optically dense layer RBC on the ramp 106 (and in the portion of the channel 94 being traversed by the light L) and treat this lower level signal as the end point of the elevated signal generated by the light detector 52 while light L passes through only the less optically dense layer PLS in the channel 94.

Thus, the pulse width of the elevated signal from the light detector 52 to the controller 18 (i.e., the time during which light L is traversing only the less optically dense layer PLS in the channel 94) is determined by the percentages of the ramp 106 that are occupied by the less optically dense layer PLS and the optically dense layer RBC. Accordingly, a greater pulse width of the signal from the light detector 52 to the controller 18 is associated with the less optically dense layer PLS occupying a larger portion of the ramp 106 (as shown in FIG. 37 from the point of view of the light source 50, which may correspond to the condition shown in FIG. 17) and will be indicative of a thinner optically dense layer RBC on the ramp 106 (and in the channel 94). Conversely, a signal from the light detector 52 to the controller 18 having a narrower pulse width is associated with the less optically dense layer PLS occupying a smaller portion of the ramp 106 (as shown in FIG. 38) and will be indicative of a thicker optically dense layer RBC on the ramp 106 (and in the channel 94).

The controller 18 may compare the pulse width of the signal to the pulse width generated during the calibration phase (described above and shown in FIG. 39), which corresponds to the pulse width when light L is transmitted to the light detector 52 over the entire width of the ramp 106. The pulse width of the signal generated by the light detector 52 during the calibration phase may be referred to as the saline calibration signal. Comparing these two pulse widths will indicate the percentage of the ramp 106 that is occupied by the less optically dense layer PLS and by the optically dense layer RBC, which information the controller 18 may use to determine the location of the interface INT within the channel 94. In particular, the interface position may be calculated as follows:

[Equation  1] Interface  position  (%) = ((saline  calibration  pulse  width − current  plasma  pulse  width)⁠/    saline  calibration  pulse  width) * 100  

It will be seen that Equation 1 effectively calculates the percentage of the ramp 106 that is occupied by the optically dense layer RBC, as the difference between the two pulse widths corresponds to the length of time that the ramp 106 is rotated through the path of the light L without the light detector 52 received an elevated level of light L (i.e., the amount of time that the ramp 106 is rotated through the path of the light L while the optically dense layer RBC is present on the ramp 106).

When the location of the interface INT on the ramp 106 has been determined, the interface control module compares the actual interface location with a desired interface location, which may be referred to as the setpoint S. The difference between the setpoint S and the calculated interface position may be referred to as the error signal E, which is shown in FIG. 40. It should be understood that so expressing the error signal E in terms of a targeted red blood cell percentage value (i.e., the percentage of the ramp 106 that is actually occupied by the optically dense layer RBC vs. the percentage of the ramp 106 which should be occupied by the optically dense layer RBC) is merely exemplary, and that the error signal E may be expressed or calculated in any of a number of other ways.

When the control value is expressed in terms of a targeted red blood cell percentage value, a negative error signal E indicates that the optically dense layer RBC on the ramp 106 is too large (as FIG. 17 shows). The interface control module of the controller 18 generates a signal to adjust an operational parameter accordingly, such as by reducing the rate at which platelet-rich plasma is removed through the first outlet 102 under action of a pump of the blood separation device 10. The interface INT moves toward the desired control position (as FIG. 16 shows), where the error signal is zero.

A positive error signal indicates that the optically dense layer RBC on the ramp 106 is too small (as FIGS. 18 and 40 show). The interface control module of the controller 18 generates a signal to adjust an operational parameter accordingly, such as by increasing the rate at which the plasma constituent is removed through the first outlet 102 under action of a pump of the blood separation device 10. The interface INT moves toward the desired control position (FIG. 16), where the error signal is again zero.

It should be understood that this system for controlling the location of the interface INT is merely exemplary and that differently configured and/or functioning systems may be employed without departing from the scope of the present disclosure.

III. Exemplary Separation Procedure

An exemplary blood separation procedure that may be carried out using systems and techniques according to the present disclosure will now be described.

Depending on the blood separation objectives, there is a suitable procedure for separating and collecting any of a variety of different blood components, either alone or in combination with other blood components. Accordingly, prior to processing, an operator selects the desired protocol (e.g., using an operator interface station, if provided), which informs the controller 18 of the manner in which it is to control the other components of the blood separation device 10 during the procedure.

The operator may also proceed to enter various parameters, such as information regarding the blood source. In one embodiment, the operator also enters the target yield for the various blood components (which may also include entering a characteristic of the blood, such as a platelet pre-count) or some other collection control system (e.g., the amount of whole blood to be processed).

If there are any fluid containers (e.g., a storage solution container) that are not integrally formed with the fluid flow circuit 12, they may be connected to the fluid flow circuit 12 (e.g., by piercing a septum of a tube of the fluid flow circuit 12 or via a luer connector), with the fluid flow circuit 12 then being mounted to the blood separation device 10 (including the fluid containers F1-F5 being hung from the weight scales W1-W6, as appropriate). An integrity check of the fluid flow circuit 12 may be executed by the controller 18 to ensure the various components are properly connected and functioning. Following a successful integrity check, the blood source is connected to the fluid flow circuit 12 and the fluid flow circuit 12 may be primed (e.g., by saline pumped from a saline bag F2 by operation of one or more of the pumps P1-P6 of the blood separation device 10).

When the fluid flow circuit 12 has been primed, blood separation may begin. The stages of blood separation vary depending on the particular procedure, and will be described in greater detail below.

A. Mononuclear Cell and Peripheral Blood Stem Cell Collection

According to one aspect of the present disclosure, the blood separation device 10 may be used to separate and collect mononuclear cells and peripheral blood stem cells.

1. Fluid Flow Circuit

FIG. 2 is a schematic view of an exemplary fluid flow circuit 12 having a pair of blood access devices (e.g., needles) for separating and collecting mononuclear cells and peripheral blood stem cells from blood. The fluid flow circuit 12 includes a cassette 48 of the type described above and illustrated in FIG. 4, which connects the various components of the fluid flow circuit 12. The various connections amongst the components of the fluid flow circuit 12 are shown in FIG. 2, which also shows the fluid flow circuit 12 mounted to the blood separation device 10.

Components of the fluid flow circuit 12 interact with many of the components of the blood separation device 10, as will be described, but there are selected components of the blood separation device 10 that are not used in separating and collecting mononuclear cells and peripheral blood stem cells using the fluid flow circuit 12 of FIG. 2. Most notably, the spinning membrane separator drive unit 14 is not used, but only the centrifugal separator 16. There are also selected valves V5, V8, and V9, the spinner pump P4, and the additive pump P6 of the blood separation device 10 that are not used in the procedure described herein. The fluid flow circuit 12 includes a fluid container F3 (which may be referred to as a waste bag) that, in the illustrated procedure of FIGS. 41-47, is only used during the pre-processing priming phase, in which saline from the saline bag F2 is pumped through the fluid flow circuit 12 to prime it, before being conveyed to the waste bag F3 for disposal at the end of the procedure.

2. MNC Collection Phase

Blood is drawn into the fluid flow circuit 12 from a blood source (e.g., using a needle) via line L1, as shown in FIG. 41. The line L1 may include a manual clamp 56 that may initially be in a closed position to prevent fluid flow through the line L1. When processing is to begin, an operator may move the manual clamp 56 from its closed position to an open position to allow fluid flow through the line L1.

The blood is drawn into the line L1 by the source pump P2. Anticoagulant from the anticoagulant bag F1 may be added to the blood via line L2 by action of the anticoagulant pump P1. The valve V10 associated with valve station C10 is open to allow flow through line L1, while the valve V3 associated with valve station C3 is closed to prevent flow through line L3, thereby directing the blood toward the centrifugal separation chamber 36 via lines L1 and L4. Prior to reaching the centrifugal separation chamber 36, the blood may pass through the air trap 62, the sensor station S2 associated with pressure sensor A2, and the centrifugal separator sensor M1. The centrifugal separator sensor M1 may detect the hematocrit of the fluid entering the centrifugal separation chamber 36 (which may be used to set the flow rate of the plasma pump P5), while the pressure sensor A2 may monitor the pressure in the centrifugal separation chamber 36.

The centrifugal separator 16 of the blood separation device 10 manipulates the centrifugal separation chamber 36 of the fluid flow circuit 12 to separate the blood in the centrifugal separation chamber 36 into platelet-rich plasma and packed red blood cells, with a mononuclear cell-containing layer or interface positioned therebetween. While the interface is referred to herein as the mononuclear cell-containing layer, it should be understood that it also contains peripheral blood stem cells, which are to be collected with the mononuclear cells. Granulocytes may tend to move into the same layers as the packed red blood cells, rather than remaining in the mononuclear cell-containing layer. In one embodiment, the centrifugal separation chamber 36 is rotated nominally at 4,500 rpm, but the particular rotational speed may vary depending on the flow rates of fluids into and out of the centrifugal separation chamber 36.

The packed red blood cells (and granulocytes) exit the centrifugal separation chamber 36 via line L5. The valve V4 associated with line L6 is closed, such that the packed red blood cells are directed through line L7. Valve V2 associated with line L8 is closed, while valve V1 is open to direct the packed red blood cells through line L9, the return line filter 58, air detector M3, and the valve station C11 associated with open valve V11 on their way to a recipient (which is typically the blood source).

Platelet-rich plasma is drawn out of the centrifugal separation chamber 36 via line L10 by the combined operation of the recirculation pump P3 and the plasma pump P5. The platelet-rich plasma travels through line L10 until it reaches a junction, which splits into lines L11 and L12. The recirculation pump P3, which is associated with line L11, redirects a portion of the platelet-rich plasma to a junction, where it mixes with blood in line L4 that is being conveyed into the centrifugal separation chamber 36 by the source pump P2. Recirculating a portion of the platelet-rich plasma into the centrifugal separation chamber 36 with inflowing blood decreases the hematocrit of the blood entering the centrifugal separation chamber 36, which may improve separation efficiency of the platelets from the red blood cells. By such an arrangement, the flow rate of the fluid entering the centrifugal separation chamber 36 is equal to the sum of the flow rates of the source pump P2 and the recirculation pump P3.

As the platelet-rich plasma drawn out of the centrifugal separation chamber 36 into line L11 by the recirculation pump P3 is immediately added back into the centrifugal separation chamber 36, the bulk or net platelet-rich plasma flow rate out of the centrifugal separation chamber 36 is equal to the flow rate of the plasma pump P5. Line L12 has a junction, where it splits into lines L13 and L14. A valve V7 associated with valve station C7 is closed to prevent fluid flow through the line L14, thereby directing the separated platelet-rich plasma through line L13 and the valve station C6 associated with open valve V6. The platelet-rich plasma in line L13 combines with the packed red blood cells in line L9, with the platelet-rich plasma being conveyed to a recipient (as described above with respect to the packed red blood cells) with the packed red blood cells as a combined fluid.

The mononuclear cell-containing layer remains within the centrifugal separation chamber 36 and increases in volume throughout this phase while the packed red blood cells and the platelet-rich plasma are removed from the centrifugal separation chamber 36. This phase continues for a predetermined amount of time or until the occurrence of a predetermined event. In one embodiment, this phase continues until a predetermined volume of blood (e.g., 1,000-2,000 ml) has been processed, which is experimentally determined to be the blood volume that can be processed before mononuclear cells begin to escape the centrifugal separation chamber 36.

Toward the end of the MNC collection phase, the valve V1 associated with valve station C1 is closed, while the valve V4 associated with valve station C4 is opened, as shown in FIG. 42. This prevents the packed red blood cells from being conveyed to the recipient (e.g., the blood source) and instead directs the packed red blood cells through line L6 and into the red blood cell collection container F4. This phase lasts long enough to collect a specific volume of packed red blood cells, which are used to transfer the mononuclear cell-containing layer out of the centrifugal separation chamber 36, as will be described in greater detail herein. In one embodiment, approximately 50 ml of packed red blood cells is collected, although the particular volume may vary without departing from the scope of the present disclosure.

3. MNC Transfer Phase

When the target volume of packed red blood cells has been collected, the MNC transfer phase begins. This phase may begin by allowing the centrifugal separator 16 to rotate the centrifugal separation chamber 36 without flow for approximately 30-60 seconds to allow the mononuclear cell distribution along the interface between the platelet-rich plasma and the red blood cell layer in the centrifugal separation chamber 36 to stabilize.

Blood draw is stopped during the MNC transfer phase by closing the valve V10 associated with valve station C10, while also ceasing operation of the anticoagulant pump P1 and the source pump P2, as shown in FIG. 43. The valve V3 associated with valve station C3 is opened to allow saline to flow out of the saline container F2 via gravity. The saline flows through line L3 and to the blood source via line L1 to prevent coagulation of any blood present in the fistula of line L1 that has not yet been anticoagulated.

To transfer the mononuclear cell-containing layer out of the centrifugal separation chamber 36, the thickness of the red blood cell layer is increased until it forces the mononuclear cell-containing layer out of the centrifugal separation chamber 36. This is done by ceasing operation of the recirculation pump P3, while the plasma pump P5 continues to operate. This pulls the packed red blood cells in the red blood cell collection container F4 via line L6. On account of valves V1 and V2 being closed, the packed red blood cells are directed back into the centrifugal separation chamber 36 via line L5 (i.e., via the red blood cell outlet).

The centrifugal separator 16 continues to rotate the centrifugal separation chamber 36 at the same speed as during the MNC collection phase (e.g., approximately 4,500 rpm), such that the returning packed red blood cells quickly increase the thickness of the red blood cell layer within the centrifugal separation chamber 36. This causes the mononuclear cell-containing layer on top of the red blood cell layer to exit the centrifugal separation chamber 36 via line L10 (i.e., the plasma outlet). It should be understood that no fluid will exit the centrifugal separation chamber 36 via line L4 (i.e., the inlet) due to the source pump P2 and the recirculation pump P3 being inactive.

The centrifugal separator sensor M1 detects the optical density and/or the redness of the fluid exiting the centrifugal separation chamber 36 via line L10. Initially, platelet-rich plasma will be exiting the centrifugal separation chamber 36 via line L10, in which case the centrifugal separator sensor M1 will observe low optical density and/or low redness. While platelet-rich plasma is exiting the centrifugal separation chamber 36 via line L10, the valve V7 associated with valve station C7 will be closed to prevent fluid flow through line L14. The valve V6 associated with valve station C6 is open, thus directing the platelet-rich plasma through line L13 for receipt by a recipient (e.g., the blood source), as described above.

Once the centrifugal separator sensor M1 detects a sufficient number of mononuclear cells exiting the centrifugal separation chamber 36 via line L10 (which corresponds to an increase in the optical density and redness of the fluid flowing through the plasma outlet), the valve V7 associated with valve station C7 opens and the valve V6 associated with valve station C6 closes, as shown in FIG. 44. This will direct the fluid in line L10 (i.e., the mononuclear cell-containing layer) through line L14 and into the MNC collection container F5.

Once the centrifugal separator sensor M1 detects that the fluid in line L10 is packed red blood cells (due to detection of an elevated optical density and/or redness level), this phase is ended to prevent packed red blood cells from flowing into the MNC collection container F5.

It should be noted that the collected red blood cells are conveyed into the centrifugal separation chamber 36 via the red blood cell outlet (i.e., line L5) to harvest mononuclear cells and peripheral blood stem cells. This is in contrast to conventional approaches, in which collected red blood cells instead enter a blood separation chamber via a whole blood inlet to harvest mononuclear cells. The approach described herein may be advantageous to the extent that a second inlet (or a fluid flow path between the red blood cell collection container and the whole blood inlet) are not required, which may reduce the number of components of the fluid flow circuit 12 and its complexity.

It should also be understood that operating the plasma pump P5 to pull the contents of the red blood cell collection container back into the centrifugal separation chamber 36 via the red blood cell outlet is only one possible approach. In another embodiment, one of the unused pumps P4 or P6 may be associated with line L5 to instead push the contents of the red blood cell collection container back into the centrifugal separation chamber 36 via line L5.

4. Plasma Flush Phase

Upon completion of the MNC transfer phase, lines L10 and L12 will contain mostly packed red blood cells (which were used to push the mononuclear cell-containing layer out of the centrifugal separation chamber 36), while line L14 will contain mononuclear cells and peripheral blood stem cells that were not conveyed all the way into the MNC collection container F5. To collect the mononuclear cells and peripheral blood stem cells in line L14, a plasma flush phase is executed.

The plasma flush phase begins by first closing the valves V4 and V7 associated with valve stations C4 and C7 (respectively), opening the valve V6 associated with valve station C6, and reestablishing separation. For an initial predetermined amount of time (e.g., approximately 10-20 seconds), anticoagulated blood is drawn into the centrifugal separation chamber 36 and separated (as in the MNC collection phase of FIGS. 41 and 42), but without operation of the recirculation pump P3 and the plasma pump P5, as shown in FIG. 45. By preventing operation of the recirculation pump P3 and the plasma pump P5, fluid will only exit the centrifugal separation chamber 36 via line L5 (i.e., the red blood cell outlet). By such a configuration, the thickness of the red blood cell layer within the centrifugal separation chamber 36 will decrease.

At the end of the MNC transfer phase, the centrifugal separation chamber 36 is substantially entirely filled with packed red blood cells (in order to push the mononuclear cell-containing layer out of the centrifugal separation chamber 36). Rather than decreasing the thickness of the red blood cell layer to the level that is typically preferred during separation (e.g., in the range of approximately 50-75% of the total fluid thickness of the centrifugal separation chamber 36, as in FIG. 16), the red blood cell layer is instead brought to a lower thickness (as in FIG. 18) in order to cause platelet-poor plasma instead of platelet-rich plasma to exit the centrifugal separation chamber 36 via line L10 (i.e., the plasma outlet). The exact thickness of the red blood cell layer may vary without departing from the scope of the present disclosure, but it may be experimentally determined as the thickness at which platelet-poor plasma (instead of platelet-rich plasma) will tend to exit the centrifugal separation chamber 36 via line L10 (i.e., the plasma outlet). In one example, the thickness of the red blood cell layer is reduced to a level that is less than half of the typically preferred thickness of the red blood cell layer during separation. In another example, the thickness of the red blood cell layer is reduced to a level (e.g., approximately 20% or less of the total fluid thickness of the centrifugal separation chamber 36) that is approximately one-third of the thickness of the red blood cell layer that is typically preferred during separation (e.g., approximately 60% of the total fluid thickness of the centrifugal separation chamber 36).

When the thickness of the red blood cell layer within the centrifugal separation chamber 36 has been reduced to a low enough level so as to produce platelet-poor plasma instead of platelet-rich plasma, the plasma pump P5 is restarted (as shown in FIG. 46). The platelet-poor plasma exiting the centrifugal separation chamber 36 via line L10 clears the packed red blood cells remaining in lines L10 and L12 at the end of the MNC transfer phase. The platelet-poor plasma pushes the packed red blood cells from lines L10 and L12 to a recipient (e.g., the blood source) via lines L13 and L9.

Once lines L10 and L12 are clear of packed red blood cells (which may be determined, for example, by a time delay after the centrifugal separator sensor M1 detects platelet-poor plasma flowing through line L10), the recirculation pump P3 is restarted, the valve V6 associated with valve station C6 closes (to prevent further platelet-poor plasma from flowing through line L13), and the valve V7 associated with valve station C7 opens (as shown in FIG. 47). This causes the platelet-poor plasma exiting the centrifugal separation chamber 36 via line L10 to flow through lines L12 and L14, which pushes the mononuclear cells and peripheral blood stem cells in line L14 (which were left there at the end of the MNC transfer phase) into the MNC collection container F5. This ensures complete collection of the mononuclear cells and peripheral blood stem cells, while minimizing the number of platelets transferred to the MNC collection container F5 (compared to the number of platelets that would end up in the MNC collection container F5 if platelet-rich plasma were instead used to flush the mononuclear cells and peripheral blood stem cells into the MNC collection container F5). This phase can also be executed at the end of the procedure to ensure that the MNC product in the MNC collection container F5 has the proper storage volume.

Restarting the recirculation pump P3 begins to aid in the reestablishment of steady state separation (by increasing the separation efficiency of platelets from red blood cells and by increasing the thickness of the red blood cell layer within the centrifugal separation chamber 36) if an additional amount of mononuclear cells and peripheral stem cells is to be collected (by transitioning back into an MNC collection phase and repeating the foregoing procedure). The centrifugal separator sensor M1 may be used to determine when platelet-rich plasma (instead of platelet-poor plasma) begins exiting the centrifugal separation chamber 36 via line L10, at which point the plasma flush phase transitions to an MNC collection phase and the procedure is repeated. The observed thickness of the red blood cell layer within the centrifugal separation chamber 36 may also be a factor in determining when to transition from the plasma flush phase to an MNC collection phase.

It should be noted that platelet-poor plasma created in the centrifugal separation chamber 36 during reestablishment of separation is used to flush mononuclear cells and peripheral blood stem cells from line L14 into the MNC collection container F5. This is in contrast to conventional approaches, in which previously collected platelet-poor plasma is instead used to flush mononuclear cells into a collection container. The approach described herein may be advantageous to the extent that a platelet-poor plasma collection container is not required, which may reduce the number of components of the fluid flow circuit 12 and its complexity. Additionally, it is not necessary to execute a platelet-poor plasma collection phase. Furthermore, following one MNC collection cycle, separation must be reestablished in both the conventional procedure and the procedure described herein. By creating and using platelet-poor plasma during a phase that must occur regardless of the approach taken, the time required to complete the procedure may be reduced.

Aspects

Aspect 1. A fluid processing system, comprising: a centrifuge configured to receive a separation chamber of a fluid processing assembly; a plurality of pumps configured to convey fluids through the fluid processing assembly; and a controller configured to actuate at least one of the plurality of pumps to convey blood into the centrifuge via an inlet, actuate the centrifuge to separate the blood in the centrifuge into a red blood cell layer, a plasma constituent, and a mononuclear cell-containing layer, actuate at least one of the plurality of pumps to convey a portion of the plasma constituent from the centrifuge via a plasma outlet and to convey a first portion of the red blood cell layer from the centrifuge via a red blood cell outlet while allowing a volume of the mononuclear cell-containing layer to increase in the centrifuge, actuate at least one of the plurality of pumps to convey a second portion of the red blood cell layer from the centrifuge via the red blood cell outlet to a red blood cell collection container of the fluid processing assembly, and actuate at least one of the plurality of pumps to convey at least a portion of the contents of the red blood cell collection container to the centrifuge via the red blood cell outlet to convey at least a portion of the mononuclear cell-containing layer out of the centrifuge for collection.

Aspect 2. The fluid processing system of Aspect 1, wherein the first portion of the red blood cell layer is at least partially returned to a blood source.

Aspect 3. The fluid processing system of any one of the preceding Aspects, wherein the portion of the plasma constituent is partially returned to a blood source.

Aspect 4. The fluid processing system of any one of the preceding Aspects, wherein the portion of the plasma constituent is partially conveyed into the centrifuge via the inlet.

Aspect 5. The fluid processing system of any one of the preceding Aspects, wherein the controller is further configured to actuate at least one of the plurality of pumps to convey plasma from the centrifuge via the plasma outlet to more fully collect said at least a portion of the mononuclear cell-containing layer.

Aspect 6. The fluid processing system of any one of the preceding Aspects, wherein the controller is further configured to actuate at least one of the plurality of pumps to convey a second portion of the plasma constituent from the centrifuge via the plasma outlet to more fully collect said at least a portion of the mononuclear cell-containing layer without the use of collected plasma.

Aspect 7. The fluid processing system of Aspect 6, wherein said portion of the plasma constituent comprises platelet-rich plasma and said second portion of the plasma constituent comprises platelet-poor plasma.

Aspect 8. The fluid processing system of any one of the preceding Aspects, wherein the controller is configured to prevent blood from entering the centrifuge while said at least a portion of the contents of the red blood cell collection container is being conveyed to the centrifuge via the red blood cell outlet and, after conveying said at least a portion of the contents of the red blood cell collection container to the centrifuge via the red blood cell outlet, actuate at least one of the plurality of pumps to convey additional blood into the centrifuge via the inlet, actuate the centrifuge to separate the additional blood in the centrifuge into an additional red blood cell layer, an additional plasma constituent, and an additional mononuclear cell-containing layer, and actuate at least one of the plurality of pumps to convey a portion of the additional plasma constituent from the centrifuge via the plasma outlet to clear red blood cells from a flow path between the centrifuge and a mononuclear cell collection container without the use of collected plasma.

Aspect 9. The fluid processing system of Aspect 8, wherein the controller is configured to, after clearing red blood cells from the flow path, actuate at least one of the plurality of pumps to convey a second portion of the additional plasma constituent from the centrifuge via the plasma outlet to more fully collect said at least a portion of the mononuclear cell-containing layer without the use of collected plasma.

Aspect 10. The fluid processing system of any one of Aspects 8-9, wherein the controller is configured to actuate the centrifuge to cause the additional red blood cell layer to have a thickness that is less than a thickness of the red blood cell layer.

Aspect 11. A method for collecting mononuclear cells, comprising: separating blood in a separation chamber into a red blood cell layer, a plasma constituent, and a mononuclear cell-containing layer; conveying a portion of the plasma constituent from the separation chamber via a plasma outlet and conveying a first portion of the red blood cell layer from the separation chamber via a red blood cell outlet while allowing a volume of the mononuclear cell-containing layer to increase in the separation chamber; conveying a second portion of the red blood cell layer from the separation chamber via the red blood cell outlet to a red blood cell collection container; and conveying at least a portion of the contents of the red blood cell collection container to the separation chamber via the red blood cell outlet to convey at least a portion of the mononuclear cell-containing layer out of the separation chamber for collection.

Aspect 12. The method of Aspect 11, wherein the first portion of the red blood cell layer is at least partially returned to a blood source.

Aspect 13. The method of any one of Aspects 11-12, wherein the portion of the plasma constituent is partially returned to a blood source.

Aspect 14. The method of any one of Aspects 11-13, wherein the portion of the plasma constituent is partially conveyed into the centrifuge via an inlet.

Aspect 15. The method of any one of Aspects 11-14, further comprising conveying plasma from the separation chamber via the plasma outlet to more fully collect said at least a portion of the mononuclear cell-containing layer.

Aspect 16. The method of any one of Aspects 11-15, further comprising conveying a second portion of the plasma constituent from the separation chamber via the plasma outlet to more fully collect said at least a portion of the mononuclear cell-containing layer without the use of collected plasma.

Aspect 17. The method of Aspect 16, wherein said portion of the plasma constituent comprises platelet-rich plasma and said second portion of the plasma constituent comprises platelet-poor plasma.

Aspect 18. The method of any one of Aspects 11-17, further comprising preventing blood from entering the separation chamber while said at least a portion of the contents of the red blood cell collection container is being conveyed to the separation chamber via the red blood cell outlet and, after conveying said at least a portion of the contents of the red blood cell collection container to the separation chamber via the red blood cell outlet, conveying additional blood into the separation chamber via an inlet, separating the additional blood in the separation chamber into an additional red blood cell layer, an additional plasma constituent, and an additional mononuclear cell-containing layer, and conveying a portion of the additional plasma constituent from the separation chamber via the plasma outlet to clear red blood cells from a flow path between the separation chamber and a mononuclear cell collection container without the use of collected plasma.

Aspect 19. The method of Aspect 18, further comprising, after clearing red blood cells from the flow path, conveying a second portion of the additional plasma constituent from the separation chamber via the plasma outlet to more fully collect said at least a portion of the mononuclear cell-containing layer without the use of collected plasma.

Aspect 20. The method of any one of Aspects 18-19, further comprising causing the additional red blood cell layer to have a thickness that is less than a thickness of the red blood cell layer.

Aspect 21. A fluid processing system, comprising: a centrifuge configured to receive a separation chamber of a fluid processing assembly; a plurality of pumps configured to convey fluids through the fluid processing assembly; and a controller configured to actuate at least one of the plurality of pumps to convey blood into the centrifuge via an inlet, actuate the centrifuge to separate the blood in the centrifuge into a red blood cell layer, a plasma constituent, and a mononuclear cell-containing layer, actuate at least one of the plurality of pumps to convey a portion of the plasma constituent from the centrifuge via a plasma outlet and to convey a first portion of the red blood cell layer from the centrifuge via a red blood cell outlet while allowing a volume of the mononuclear cell-containing layer to increase in the centrifuge, actuate at least one of the plurality of pumps to convey a second portion of the red blood cell layer from the centrifuge via the red blood cell outlet to a red blood cell collection container of the fluid processing assembly, actuate at least one of the plurality of pumps to convey at least a portion of the contents of the red blood cell collection container to the centrifuge to convey at least a portion of the mononuclear cell-containing layer out of the centrifuge via the plasma outlet for collection, and actuate at least one of the plurality of pumps to convey plasma from the centrifuge via the plasma outlet to more fully collect said at least a portion of the mononuclear cell-containing layer without the use of collected plasma.

Aspect 22. The fluid processing system of Aspect 21, wherein the first portion of the red blood cell layer is at least partially returned to a blood source.

Aspect 23. The fluid processing system of any one of Aspects 21-22, wherein the portion of the plasma constituent is partially returned to a blood source.

Aspect 24. The fluid processing system of any one of Aspects 21-23, wherein the portion of the plasma constituent is partially conveyed into the centrifuge via the inlet.

Aspect 25. The fluid processing system of any one of Aspects 21-24, wherein the portion of the plasma constituent comprises platelet-rich plasma and the plasma conveyed from the centrifuge via the plasma outlet to more fully collect said at least a portion of the mononuclear cell-containing layer comprises platelet-poor plasma.

Aspect 26. The fluid processing system of any one of Aspects 21-25, wherein the controller is configured to prevent blood from entering the centrifuge while said at least a portion of the contents of the red blood cell collection container is being conveyed to the centrifuge and, after conveying said at least a portion of the contents of the red blood cell collection container to the centrifuge, actuate at least one of the plurality of pumps to convey additional blood into the centrifuge via the inlet, and actuate the centrifuge to separate the additional blood in the centrifuge into an additional red blood cell layer, an additional plasma constituent, and an additional mononuclear cell-containing layer, wherein the plasma conveyed from the centrifuge via the plasma outlet to more fully collect said at least a portion of the mononuclear cell-containing layer comprises a second portion of the additional plasma constituent.

Aspect 27. The fluid processing system of Aspect 26, wherein the controller is configured to actuate at least one of the plurality of pumps to convey a first portion of the additional plasma constituent from the centrifuge via the plasma outlet to clear red blood cells from a flow path between the centrifuge and a mononuclear cell collection container without the use of collected plasma before the second portion of the additional plasma constituent is conveyed from the centrifuge.

Aspect 28. The fluid processing system of Aspect 27, wherein the controller is configured to actuate at least one of the plurality of pumps to return the red blood cells cleared from the flow path to a blood source.

Aspect 29. The fluid processing system of any one of Aspects 26-28, wherein the controller is configured to actuate the centrifuge to cause the additional red blood cell layer to have a thickness that is less than a thickness of the red blood cell layer.

Aspect 30. The fluid processing system of any one of Aspects 21-29, wherein said at least a portion of the contents of the red blood cell collection container is conveyed to the centrifuge via the red blood cell outlet.

Aspect 31. A method for collecting mononuclear cells, comprising: separating blood in a separation chamber into a red blood cell layer, a plasma constituent, and a mononuclear cell-containing layer; conveying a portion of the plasma constituent from the separation chamber via a plasma outlet and conveying a first portion of the red blood cell layer from the separation chamber via a red blood cell outlet while allowing a volume of the mononuclear cell-containing layer to increase in the separation chamber; conveying a second portion of the red blood cell layer from the separation chamber via the red blood cell outlet to a red blood cell collection container; conveying at least a portion of the contents of the red blood cell collection container to the separation chamber to convey at least a portion of the mononuclear cell-containing layer out of the separation chamber for collection; and conveying plasma from the separation chamber via the plasma outlet to more fully collect said at least a portion of the mononuclear cell-containing layer without the use of collected plasma.

Aspect 32. The method of Aspect 31, wherein the first portion of the red blood cell layer is at least partially returned to a blood source.

Aspect 33. The method of any one of Aspects 31-32, wherein the portion of the plasma constituent is partially returned to a blood source.

Aspect 34. The method of any one of Aspects 31-33, wherein the portion of the plasma constituent is partially conveyed into the separation chamber via an inlet.

Aspect 35. The method of any one of Aspects 31-34, wherein the portion of the plasma constituent comprises platelet-rich plasma and the plasma conveyed from the separation chamber via the plasma outlet to more fully collect said at least a portion of the mononuclear cell-containing layer comprises platelet-poor plasma.

Aspect 36. The method of any one of Aspects 31-35, wherein blood is prevented from entering the separation chamber while said at least a portion of the contents of the red blood cell collection container is being conveyed to the separation chamber and further comprising, after conveying said at least a portion of the contents of the red blood cell collection container to the separation chamber, conveying additional blood into the separation chamber via an inlet, and separating the additional blood in the separation chamber into an additional red blood cell layer, an additional plasma constituent, and an additional mononuclear cell-containing layer, wherein the plasma conveyed from the separation chamber via the plasma outlet to more fully collect said at least a portion of the mononuclear cell-containing layer comprises a second portion of the additional plasma constituent.

Aspect 37. The method of Aspect 36, further comprising conveying a first portion of the additional plasma constituent from the separation chamber via the plasma outlet to clear red blood cells from a flow path between the separation chamber and a mononuclear cell collection container without the use of collected plasma before the second portion of the additional plasma constituent is conveyed from the separation chamber.

Aspect 38. The method of Aspect 37, wherein the red blood cells cleared from the flow path are returned to a blood source.

Aspect 39. The method of any one of Aspects 36-38, wherein the additional red blood cell layer has a thickness that is less than a thickness of the red blood cell layer.

Aspect 40. The method of any one of Aspects 31-39, wherein said at least a portion of the contents of the red blood cell collection container is conveyed to the separation chamber via the red blood cell outlet.

It will be understood that the embodiments and examples described above are illustrative of some of the applications of the principles of the present subject matter. Numerous modifications may be made by those skilled in the art without departing from the spirit and scope of the claimed subject matter, including those combinations of features that are individually disclosed or claimed herein. For these reasons, the scope hereof is not limited to the above description but is as set forth in the following claims, and it is understood that claims may be directed to the features hereof, including as combinations of features that are individually disclosed or claimed herein. 

1-10. (canceled)
 11. A method for collecting mononuclear cells, comprising: separating blood in a separation chamber into a red blood cell layer, a plasma constituent, and a mononuclear cell-containing layer; conveying a portion of the plasma constituent from the separation chamber via a plasma outlet and conveying a first portion of the red blood cell layer from the separation chamber via a red blood cell outlet while allowing a volume of the mononuclear cell-containing layer to increase in the separation chamber; conveying a second portion of the red blood cell layer from the separation chamber via the red blood cell outlet to a red blood cell collection container; and conveying at least a portion of the contents of the red blood cell collection container to the separation chamber via the red blood cell outlet to convey at least a portion of the mononuclear cell-containing layer out of the separation chamber for collection.
 12. The method of claim 11, wherein the first portion of the red blood cell layer is at least partially returned to a blood source.
 13. The method of claim 11, wherein the portion of the plasma constituent is partially returned to a blood source.
 14. The method of claim 11, wherein the portion of the plasma constituent is partially conveyed into the centrifuge via an inlet.
 15. The method of claim 11, further comprising conveying plasma from the separation chamber via the plasma outlet to more fully collect said at least a portion of the mononuclear cell-containing layer.
 16. The method of claim 11, further comprising conveying a second portion of the plasma constituent from the separation chamber via the plasma outlet to more fully collect said at least a portion of the mononuclear cell-containing layer without the use of collected plasma.
 17. The method of claim 16, wherein said portion of the plasma constituent comprises platelet-rich plasma and said second portion of the plasma constituent comprises platelet-poor plasma.
 18. The method of claim 11, further comprising preventing blood from entering the separation chamber while said at least a portion of the contents of the red blood cell collection container is being conveyed to the separation chamber via the red blood cell outlet and, after conveying said at least a portion of the contents of the red blood cell collection container to the separation chamber via the red blood cell outlet, conveying additional blood into the separation chamber via an inlet, separating the additional blood in the separation chamber into an additional red blood cell layer, an additional plasma constituent, and an additional mononuclear cell-containing layer, and conveying a portion of the additional plasma constituent from the separation chamber via the plasma outlet to clear red blood cells from a flow path between the separation chamber and a mononuclear cell collection container without the use of collected plasma.
 19. The method of claim 18, further comprising, after clearing red blood cells from the flow path, conveying a second portion of the additional plasma constituent from the separation chamber via the plasma outlet to more fully collect said at least a portion of the mononuclear cell-containing layer without the use of collected plasma.
 20. The method of claim 18, further comprising causing the additional red blood cell layer to have a thickness that is less than a thickness of the red blood cell layer. 21-30. (canceled)
 31. A method for collecting mononuclear cells, comprising: separating blood in a separation chamber into a red blood cell layer, a plasma constituent, and a mononuclear cell-containing layer; conveying a portion of the plasma constituent from the separation chamber via a plasma outlet and conveying a first portion of the red blood cell layer from the separation chamber via a red blood cell outlet while allowing a volume of the mononuclear cell-containing layer to increase in the separation chamber; conveying a second portion of the red blood cell layer from the separation chamber via the red blood cell outlet to a red blood cell collection container; conveying at least a portion of the contents of the red blood cell collection container to the separation chamber to convey at least a portion of the mononuclear cell-containing layer out of the separation chamber for collection; and conveying plasma from the separation chamber via the plasma outlet to more fully collect said at least a portion of the mononuclear cell-containing layer without the use of collected plasma.
 32. The method of claim 31, wherein the first portion of the red blood cell layer is at least partially returned to a blood source.
 33. The method of claim 31, wherein the portion of the plasma constituent is partially returned to a blood source.
 34. The method of claim 31, wherein the portion of the plasma constituent is partially conveyed into the separation chamber via an inlet.
 35. The method of claim 31, wherein the portion of the plasma constituent comprises platelet-rich plasma and the plasma conveyed from the separation chamber via the plasma outlet to more fully collect said at least a portion of the mononuclear cell-containing layer comprises platelet-poor plasma.
 36. The method of wherein blood is prevented from entering the separation chamber while said at least a portion of the contents of the red blood cell collection container is being conveyed to the separation chamber and further comprising, after conveying said at least a portion of the contents of the red blood cell collection container to the separation chamber, conveying additional blood into the separation chamber via an inlet, and separating the additional blood in the separation chamber into an additional red blood cell layer, an additional plasma constituent, and an additional mononuclear cell-containing layer, wherein the plasma conveyed from the separation chamber via the plasma outlet to more fully collect said at least a portion of the mononuclear cell-containing layer comprises a second portion of the additional plasma constituent.
 37. The method of claim 36, further comprising conveying a first portion of the additional plasma constituent from the separation chamber via the plasma outlet to clear red blood cells from a flow path between the separation chamber and a mononuclear cell collection container without the use of collected plasma before the second portion of the additional plasma constituent is conveyed from the separation chamber.
 38. The method of claim 37, wherein the red blood cells cleared from the flow path are returned to a blood source.
 39. The method of claim 36, wherein the additional red blood cell layer has a thickness that is less than a thickness of the red blood cell layer.
 40. The method of claim 31, wherein said at least a portion of the contents of the red blood cell collection container is conveyed to the separation chamber via the red blood cell outlet. 